Assessment of environmental pollution of heavy metals deposited on the leaves of trees at Yazd bus terminals

Abstract

There is a lack of information on the effect of urban transport activities in emitting heavy elements into the environment. This research assesses the concentrations of some heavy elements in the deposited atmospheric dust at Yazd bus terminals in Yazd, Iran. So, 34 falling dust samples were collected from the leaves of trees planted near the bus terminals. Following the digestion by nitric acid, the total concentrations of cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), chromium ‬(Cr), and manganese (Mn) were determined in the dust by atomic absorption spectrometry. The map representing the spatial distribution of the metals was plotted, and their sources were identified using Pearson's correlation coefficient, principal component analysis, and cluster analysis. The results indicated that the mean concentrations of the heavy metals in the dust deposited on the tree leaves were in the order of Cd < Co < Ni < Pb < Cu < Zn < Cr < Mn. The map representing the spatial distribution of the heavy metal concentrations illustrated that the abundance of metals in different stations varied with their location. Two main sources were detected for the heavy metals in the deposited dust. Co, Cd, Mn, and Ni had anthropogenic and lithogenic sources while Pb, Zn, Cr, and Cu were emitted by traffic and industrial activities. Enrichment factor, contamination factor, integrated pollution index, and risk index were estimated at low to extremely high levels of pollution in residential, commercial, green space, and environmental uses. Based on the results, the growth of industrialization and human activities contribute to the heavy metal contamination of the environment emitted into the atmosphere in Yazd.

Keywords: Cluster Analysis; Falling dust; Pollution index; Principal Component Analysis.